The cell body (soma) of the primary sensory neuron and initial axonal segment are enveloped by a sheath that consists of discrete satellite glial cells each with its own plasma membrane. We know little of the physiological properties of the glia in the dorsal root ganglion and what signals they send and receive. By analogy with astrocytes, it is possible that satellite glia engage in bi-directional ionic and chemical communication with the neurons they ensheathe and with non-neuronal cells. A major question is whether satellite glia have different functional properties according to whether their neurons have nociceptive or non-nociceptive properties. Another question is whether abnormal properties of satellite glia play a role in neuropathic pain by contributing to neuronal hyperexcitability and ectopic discharges originating in the ganglion after trauma or inflammation. With this R21 we explore the novel application of electrophysiology and imaging to the study of the physiological properties of the satellite glia of functionally identified sensory neurons in the rat. We will carry out patch-clamp electrophysiological recording (in vitro), and imaging of calcium signals (in vivo), in satellite glia of visualized neuronal somata. Using intracellular recording from the neuronal soma, we will link the properties of the neuron with the properties of the attached glia and search for bi-directional communication between the two cell types. In addition, we will explore the possibility that these glial properties and possible glial-neuronal interactions are significantly altered after a chronic compression of the dorsal root ganglion (CCD model of neuropathic pain) - an injury known to enhance the excitability of neuronal cell bodies and to produce allodynia and hyperalgesia. The R21 is intended to generate preliminary data and new hypotheses on the physiological properties of satellite glia and their relationships with their sensory neurons in the context of normal and neuropathic mechanisms of pain. [unreadable] [unreadable]